Energy efficient data center liquid cooling with geothermal enhancement

ABSTRACT

A data center cooling system is operated in a first mode, has an indoor portion wherein heat is absorbed from components in the data center by a heat transfer fluid, and has an outdoor heat exchanger portion and a geothermal heat exchanger portion. The first mode includes ambient air cooling of the heat transfer fluid in the outdoor heat exchanger portion and/or geothermal cooling of the heat transfer fluid in the geothermal heat exchanger portion. Based on an appropriate metric, a determination is made that a switch should be made from the first mode to a second, different, mode; and, responsive thereto, the data center cooling system is switched to the second mode. The second mode includes at least another of ambient air cooling of the heat transfer fluid in the outdoor heat exchanger portion and geothermal cooling of the heat transfer fluid in the geothermal heat exchanger portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.15/803,755 filed Nov. 4, 2017, and entitled ENERGY EFFICIENT DATA CENTERLIQUID COOLING WITH GEOTHERMAL ENHANCEMENT, which is in turn a divisionof U.S. patent application Ser. No. 13/252,888 filed 4 Oct. 2011, andentitled ENERGY EFFICIENT DATA CENTER LIQUID COOLING WITH GEOTHERMALENHANCEMENT, now U.S. Pat. No. 9,811,126. The complete disclosure ofU.S. patent application Ser. Nos. 15/803,755 and 13/252,888 areexpressly incorporated herein by reference in their entireties for allpurposes.

STATEMENT OF GOVERNMENT RIGHTS

This invention was made with Government support under Contract No.:DE-EE0002894 awarded by the Department of Energy (DOE). The Governmenthas certain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to the thermodynamic arts, and, moreparticularly, to thermal control of computer equipment and the like.

BACKGROUND OF THE INVENTION

Economizer based ambient cooling of data centers has been proposed as atechnique to reduce data center power consumption. Economizer basedambient cooling of data centers is typically limited to winter monthsand requires refrigeration based cooling during hot temperature months.In any locale where temperatures below freezing are anticipated, anantifreeze solution (typically glycol based) is required within thecoolant loop that is exposed to the ambient environment to avoidfreeze-up if the loop circulation stops for any reason. This antifreezesolution is not as effective in thermal transport as water alone, withthe degree of ineffectiveness varying depending on the exact characterof the devices putting heat into the coolant loop. This lower efficiencycan be significant when attempting to allow for ambient air cooling athigh ambient temperatures.

SUMMARY OF THE INVENTION

Principles of the invention provide techniques for energy efficient datacenter liquid cooling with geothermal enhancement. In one aspect, anexemplary method includes the step of operating a data center coolingsystem in a first mode. The data center cooling system has an indoorportion wherein heat is absorbed from components in the data center by aheat transfer fluid. The data center cooling system has an outdoor heatexchanger portion and a geothermal heat exchanger portion. The firstmode includes at least one of: ambient air cooling of the heat transferfluid in the outdoor heat exchanger portion; and geothermal cooling ofthe heat transfer fluid in the geothermal heat exchanger portion.Further steps include determining, based on an appropriate metric, thata switch should be made from the first mode to a second mode; and,responsive to the determining, switching the data center cooling systemto the second mode. The second mode is different than the first mode.The second mode includes at least another one of: ambient air cooling ofthe heat transfer fluid in the outdoor heat exchanger portion; andgeothermal cooling of the heat transfer fluid in the geothermal heatexchanger portion.

In another aspect, an exemplary data center cooling system includes anindoor portion wherein heat is absorbed from components in the datacenter by a heat transfer fluid; an outdoor heat exchanger portion inselective fluid communication with the indoor portion; a geothermal heatexchanger portion in selective fluid communication with the indoorportion; and a valve arrangement configured to switch the data centercooling system between first and second modes of operation. The firstmode includes at least one of: ambient air cooling of the heat transferfluid in the outdoor heat exchanger portion; and geothermal cooling ofthe heat transfer fluid in the geothermal heat exchanger portion. Thesecond mode is different than the first mode and includes at leastanother one of: ambient air cooling of the heat transfer fluid in theoutdoor heat exchanger portion; and geothermal cooling of the heattransfer fluid in the geothermal heat exchanger portion.

In still another aspect, a data center cooling system includes an indoorportion wherein heat is absorbed from electronic components in the datacenter by a heat transfer fluid; and a geothermal heat exchanger portionin thermal communication with the indoor portion and configured toreject the heat to at least one of earth and groundwater.

As used herein, “facilitating” an action includes performing the action,making the action easier, helping to carry the action out, or causingthe action to be performed. Thus, by way of example and not limitation,instructions executing on one processor might facilitate an actioncarried out by instructions executing on a remote processor, by sendingappropriate data or commands to cause or aid the action to be performed;or by sending signals to control a valve, fan, or the like, based onsensed temperature, pressure, flow, or the like. For the avoidance ofdoubt, where an actor facilitates an action by other than performing theaction, the action is nevertheless performed by some entity orcombination of entities.

One or more embodiments of the invention or elements thereof (forexample, system control and/or system design) can be implemented in theform of, or otherwise facilitated by, a computer program productincluding a computer readable storage medium with computer usableprogram code for performing the method steps indicated. Furthermore, oneor more embodiments of the invention or elements thereof can beimplemented in the form of a system (or apparatus) including a memory,and at least one processor that is coupled to the memory and operativeto perform exemplary method steps. Yet further, in another aspect, oneor more embodiments of the invention or elements thereof can beimplemented in the form of means for carrying out one or more of themethod steps described herein; the means can include (i) hardwaremodule(s), (ii) software module(s) stored in a computer readable storagemedium (or multiple such media) and implemented on a hardware processor,or (iii) a combination of (i) and (ii); any of (i)-(iii) implement thespecific techniques set forth herein. Examples of use of a computerprogram product or computer-related means include sending signals tocontrol a valve, fan, or the like, based on sensed temperature,pressure, flow, heat dissipation, or the like; and/or use of a computerfor computer-aided system design.

Techniques of the present invention can provide substantial beneficialtechnical effects. In one or more embodiments, a significant technicalbenefit is the ability to provide cooling to a data center year round inany geography. For ambient air cooling in high ambient temperatureenvironments, a geothermal loop can significantly enhance the coolingperformance by providing additional heat dissipation to the ambient(surroundings).

These and other features and advantages of the present invention willbecome apparent from the following detailed description of illustrativeembodiments thereof, which is to be read in connection with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary data center liquid cooling system, accordingto an aspect of the invention;

FIGS. 2-4 show four stages in operation of the system of FIG. 1;

FIG. 5 shows a flow chart for operation of the system of FIG. 1;

FIG. 6 shows another exemplary data center liquid cooling system,according to an aspect of the invention;

FIGS. 7-9 show four stages in operation of the system of FIG. 6;

FIG. 10 shows a flow chart for operation of the system of FIG. 6;

FIG. 11 shows still another exemplary data center liquid cooling system,according to an aspect of the invention;

FIGS. 12-14 show four stages in operation of the system of FIG. 11;

FIG. 15 shows a flow chart for operation of the system of FIG. 11;

FIG. 16 shows yet another exemplary data center liquid cooling system,according to an aspect of the invention;

FIGS. 17-19 show four stages in operation of the system of FIG. 16;

FIG. 20 shows a flow chart for operation of the system of FIG. 16;

FIG. 21 shows a further exemplary data center liquid cooling system,according to an aspect of the invention;

FIGS. 22-24 show four stages in operation of the system of FIG. 21;

FIG. 25 shows a flow chart for operation of the system of FIG. 21;

FIG. 26 shows a still further exemplary data center liquid coolingsystem, according to an aspect of the invention;

FIGS. 27-29 show four stages in operation of the system of FIG. 26;

FIG. 30 shows a flow chart for operation of the system of FIG. 26;

FIGS. 31-33 show three even further exemplary data center liquid coolingsystems, according to aspects of the invention;

FIG. 34 shows US average ground water temperature; and

FIG. 35 depicts a computer system that may be useful in implementing oneor more aspects and/or elements of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

As noted, economizer based ambient cooling of data centers has beenproposed as a technique to reduce data center power consumption.Economizer based ambient cooling of data centers is typically limited towinter months and requires refrigeration based cooling during hottemperature months. In one or more embodiments, to eliminate the needfor refrigeration based cooling, a liquid based system which uses theambient environment can be used, and can be enhanced via a geothermalliquid cooling loop which can operate as needed, and can be placed inparallel or series.

In any locale where temperatures below freezing are anticipated, anantifreeze solution (typically glycol based) is required within thecoolant loop that is exposed to the ambient environment to avoidfreeze-up if the loop circulation stops for any reason. This antifreezesolution is not as effective in thermal transport as water alone, withthe degree of ineffectiveness varying depending on the exact characterof the devices putting heat into the coolant loop. This lower efficiencycan be significant when attempting to allow for ambient air cooling athigh ambient temperatures. In one or more embodiments, with the additionof a geothermal liquid cooling loop, thermal performance of ambient aircooling at high ambient temperatures can be significantly enhanced.

In one or more instances, a geothermal loop is added to an ambientliquid cooling solution for data centers. For ambient air cooling inhigh ambient temperature environments, a geothermal loop cansignificantly enhance the cooling performance by enhancing the heatdissipation to the ambient (surroundings). For ambient air cooling invery low ambient temperature environments, a geothermal loop can helpmaintain the liquid going to the system at certain minimum temperature.

In one or more embodiments, the system is implemented by adding a seriesof three-way valves (which can be computer controlled) to incorporate ageothermal liquid cooling loop into an ambient liquid cooling solutionfor data centers. The geothermal loop can be incorporated either in aseries or in a parallel arrangement giving flexibility to operate atmore than more stage. One or more embodiments can work in three stages(also referred to as modes):

-   -   (1) completely in geothermal cooling mode,    -   (2) completely in ambient air cooling mode, and    -   (3) Dual/Hybrid mode wherein both geothermal cooling and ambient        air cooling mode are active.

The following figures explain the working and implementation of one ormore non-limiting exemplary embodiments of systems with geothermalenhancement for liquid cooled data centers.

FIG. 1 shows a way of implementing an exemplary embodiment in a liquidcooled data center 100 with an air side outdoor heat exchanger 103(optionally also including fan 105 but could in some instances use freeconvection). The system being cooled includes a liquid cooled rack 104and a side car segment 106 (the side car segment is an air-to-liquidheat exchanger, basically a radiator similar to a car's radiator) and ispresent inside the data center 100. The liquid pump 111 can either beplaced inside the data center unit or outside. The geothermal loop 199is connected to the ambient air cooling loop 197 in a parallelarrangement with the help of three-way valves 195, 193. These three-wayvalves can be computer controlled. In case of computer controlledthree-way valves, the outside air temperature T_(O) measured by sensor109, ground temperature TG measured by sensor 191, and the temperatureof the liquid entering the data center system T measured by sensor 189can be used as control parameters for the three-way valve controltechnique. The working of this particular implementation isschematically explained through FIG. 2-FIG. 5. Note geothermal coil 187for dissipating heat below ground level and optional booster pump 185.Note also system heat dissipation sensor Q_(SYS) 183. In the case ofcomputer controlled three-way valves, in addition to the measuredtemperatures, system heat dissipation sensor QSYS 183 can alsooptionally be used as a control parameter for the three-way valvecontrol technique.

The dots 9999 in the figures represent pipe connectors and the gapthere-between is not intended to suggest a physical gap in the pipes,but rather to delineate that the portion of the given figure that is onthe left of the dots represents an information technology (IT) rackwhile the portion of the given figure on the right of the dots representthe piping scheme for the coolant switch operation of one or moreembodiments.

Non-limiting examples of coolants include water and glycol. FIG. 1represents a closed loop geothermal cooling parallel arrangement.Geothermal coil 187 is used to dissipate heat below ground level. In atleast some cases, coil 187 is at least 2 m below ground level. Theground level temperature may vary, for example, from about 42 F to about80 F, depending on location. See discussion with respect to FIG. 34below.

FIG. 2 represents Stage 1A in which only the geothermal loop 199 isactive and the ambient air cooling loop 197 is inactive. Depending uponthe required coolant flow rate, the booster pump 185 can be either ON orOFF. The outside heat exchanger 103 is OFF (as is fan 105 if present)and the 3-way valves 193, 195 are completely turned so as to allow flowonly through the geothermal loop.

FIG. 3 represents Stage 1B in which both the geothermal cooling 199 andambient air cooling 197 loops are active. Again, depending upon therequired coolant flow rate, the booster pump 185 can either be ON orOFF. The outside heat exchanger 103 is ON (as is fan 105 if present) andthe 3-way valves 193, 195 are partially turned so as to allow flowthrough both the geothermal and ambient air cooling loops.

FIG. 4 represents Stage 1C in which only the ambient air cooling loop197 is active and the geothermal loop 199 is inactive. The outside heatexchanger 103 is ON (as is fan 105 if present) and the 3-way valves 193,195 are completely turned to allow flow only through the ambient aircooling loop. Since there no flow through the geothermal loop, thebooster pump 185 remains OFF.

FIG. 5 is a flowchart 500 that illustrates a non-limiting exemplaryoperational procedure for the geothermal cooling enhancement arrangementof FIGS. 1-4. The cooling system can be initiated from any stage.However, for simplicity, Stage 1A (FIG. 2) is represented as the initialstate of the cooling system, as at 502. The outdoor air temperatureT_(O), the ground temperature TG and the temperature T of the liquidentering the data center system are constantly monitored. Based on thesetemperatures, different stages of the scheme can be activated. As seenat step 504, if T is less than T₁, simply continue to operate in stage1A, as seen at step 506, per the “Y” branch of decision block 504.

When the temperature of the liquid entering the data center is higherthan the maximum allowed temperature for liquid entering the data center(T₁), as per the “N” branch of decision block 504, the geothermal loopalone is not capable of dissipating the heat to the surroundings and thecooling system requires a different stage of operation. In thissituation, a check is made whether the outside air temperature is higherthan the ground temperature, as at 508. If yes, the ambient air coolingloop will also be activated (that is, Stage 1B, FIG. 3), as per step 516from the “Y” branch of block 508. If No, the ambient air cooling loopwill be activated and the geothermal loop will be deactivated (that is,Stage 1C, FIG. 4), as per step 510 and the “N” branch of decision block508. If, at this stage, the temperature of the liquid entering the datacenter is higher than the maximum allowed temperature (T₁), as per the“N” branch of decision block 512, then the ambient air cooling loop onlyis also not capable of dissipating the heat to the surroundings and thecooling system requires the dual (hybrid) stage of operation (that is,Stage 1B, FIG. 3) as per step 516 reached via the “N” branch of block512. If, on the other hand, the temperature of the liquid entering thedata center is not higher than the maximum allowed temperature (T₁), asper the “Y” branch of decision block 512, then continue with Stage 1C,FIG. 4, as per step 514.

Considering again step 516, once the system is in the hybrid mode ofoperation, it will continually check whether the temperature of theliquid entering the data center system is higher than a minimumtemperature allowed for liquid entering the data center when both loopsare operational (T₂), as at 518. If so, continue in hybrid mode as perthe N branch of decision block 518. If not, as per the “Y” branch ofblock 518, either of the other two modes will be activated based on theoutdoor air and ground temperature, as indicated at 520, 522. Inparticular, if the ground temperature is not less than T_(O), as per theN branch of block 520, then proceed to step 510 for operation in stage1C. If the ground temperature is less than T_(O), as per the Y branch ofblock 520, then proceed to step 522 for operation in stage 1A.

The switching between different modes of operation can take place Nnumber of times a year depending upon the location of the system,weather conditions of the location, and other environmental factors. Ingeneral, N is a positive integer.

FIG. 6 shows an alternative embodiment having a series arrangement in aliquid cooled data center 100 with an air side outdoor heat exchanger.In general, similar elements in the figures have a similar referencecharacter and are not necessarily described again in each figure, andsimilar variables in the figures have a similar variable name. Thesystem being cooled includes a liquid cooled rack 104 and a side carsegment 106 and is present inside the data center 100. The liquid pump111 can either be placed inside the data center unit or outside. Thegeothermal loop 199 is connected to the ambient air cooling loop 197 ina series arrangement with the help of three-way valves 693, 695. Thesethree-way valves can be computer controlled. In case of computercontrolled three-way valves, the outside air temperature, the groundtemperature and the temperature of the liquid entering the data centersystem can be used as control parameters for the three-way valve controltechnique. The working of this particular exemplary embodiment isschematically explained through FIG. 7-FIG. 10.

Non-limiting examples of coolants include water and glycol. FIG. 6represents a closed loop geothermal cooling series arrangement.Geothermal coil 187 is used to dissipate heat below ground level. In atleast some cases, coil 187 is at least 2 m below ground level. Theground level temperature may vary, for example, from about 42 F to about80 F, depending on location. See discussion with respect to FIG. 34below.

FIG. 7 represents Stage 2A in which only the geothermal loop 199 isactive and the ambient air cooling loop 197 is inactive. Depending uponthe required coolant flow rate, the optional booster pump 185 can beeither ON or OFF. The outside heat exchanger 103 is OFF (as is the fan105 if present) and the three-way valves 693, 695 are completely turnedso as to allow flow through the geothermal loop.

FIG. 8 represents Stage 2B in which both the geothermal cooling 199 andthe ambient air cooling 197 loops are active. Again, depending upon therequired coolant flow rate, the booster pump 185 can either be ON orOFF. The outside heat exchanger 103 is ON (as is fan 105 if present) andthe three-way valves 693, 695 are completely turned so as to allow flowthrough both the geothermal and ambient air cooling loops.

FIG. 9 represents Stage 2C in which only the ambient air cooling loop197 is active and the geothermal loop 199 is inactive. The outside heatexchanger 103 is ON (as is fan 105 if present) and the three-way valves693, 695 are completely turned to stop the flow through the geothermalcooling loop and to allow flow only through the ambient air coolingloop. Since there no flow through the geothermal loop, the optionalbooster pump 185 remains OFF.

FIG. 10 is a flowchart 1000 that illustrates a non-limiting exemplaryoperational procedure for the geothermal cooling enhancement arrangementof FIGS. 6-9. The cooling system can be initiated from any stage,however, for simplicity, Stage 2A (FIG. 7) is represented as the initialstate of the cooling system, as per 1002. The outdoor air temperature,the ground temperature and the temperature of the liquid entering thedata center system are constantly monitored and based on thesetemperatures, different stages can be activated. When the temperature ofthe liquid entering the data center is higher than the maximum allowedtemperature (T₁), as per the “N” branch of decision block 1004, thegeothermal loop only is not capable of dissipating the heat to thesurroundings and the cooling system requires a different stage ofoperation (otherwise, as per the “Y” branch of decision block 1004,simply continue with stage 2A as at 1005).

Following the “N” branch of block 1004, a check is made, at decisionblock 1008, whether the outside air temperature is higher than theground temperature. If yes (“Y” branch of block 1008), the ambient aircooling loop will also be activated (that is, Stage 2B, FIG. 8), as perstep 1016. If no (“N” branch of block 1008), the ambient air coolingloop will be activated and the geothermal loop will be deactivated (thatis, Stage 2C, FIG. 9), as per step 1010. If at this stage, thetemperature of the liquid entering the data center is higher than themaximum allowed temperature (T₁) (“N” branch of block 1012), then, theambient air cooling loop only is also not capable of dissipating theheat to the surrounding and the cooling system requires the dual(hybrid) stage (mode) of operation (that is, Stage 2B, FIG. 8), as perstep 1016 (otherwise simply continue in stage 2C as per 1013 reachedfrom “Y” branch of block 1012). Once the system is in the hybrid mode ofoperation, it will continually check whether the temperature of theliquid entering the data center system is higher than a minimumtemperature (T₂), as per step 1018 (if higher than minimum, keepchecking as per “N” branch of block 1018). If not (“Y” branch of block1018), either of the other two modes will be activated based on theoutdoor air and ground temperature, as per steps 1020, 1022. Inparticular, if the ground temperature is not less than the outsidetemperature, as per the “N” branch of decision block 1020, proceed tostep 1010 for operation in stage 2C; otherwise, proceed to step 1022 foroperation in stage 2A via “Y” branch of block 1020.

The switching between different modes of operation can take place Nnumber of times a year depending upon location of the system, weatherconditions of the location, and other environmental factors.

FIG. 11 shows another alternative embodiment. The system being cooledincludes a liquid cooled rack 104 and a side car segment 106 and ispresent inside the data center. The liquid pump 111 can either be placedinside the data center unit or outside. The geothermal loop 1199 in thisparticular configuration uses the ground water for dissipating thesystem heat to the surroundings. The geothermal loop is connected to theambient air cooling loop 1197 in a parallel arrangement with the help ofthree-way valves 1193, 1195. These three-way valves can be computercontrolled. In case of computer controlled three-way valves, the outsideair temperature, the ground temperature and the temperature of theliquid entering the data center system can be used as control parametersfor the three-way valve control technique. In a preferred approach,there are two temperature sensors associated with the liquid passingthrough the heat exchanger 102—one 1151 at the inlet to the outside airheat exchanger and the other (omitted to avoid clutter) at the outletfrom the outside air heat exchanger. These two sensors will be used tomonitor the amount of heat dissipated to the outside air through theheat exchanger. Also based on this information the position of thethree-way valve can be controlled. Note that geothermal loop 1199includes upper loop 1198 and lower (ground water) loop 1196 thermallycoupled by liquid-to-liquid heat exchanger 1194.

Non-limiting examples of coolants include water and glycol. FIG. 11represents an open loop geothermal cooling parallel arrangement. In atleast some cases, groundwater is taken from at least 2 m below groundlevel. The ground level temperature may vary, for example, from about 42F to about 80 F, depending on location. See discussion with respect toFIG. 34 below.

The working of this particular implementation is schematically explainedthrough FIGS. 12-15.

FIG. 12 represents Stage 3A in which only the geothermal loop 1199 isactive and the ambient air cooling loop 1197 is inactive. Pump-2 1255 isON, the outside heat exchanger 103 (and fan 105 if present) is/are OFFand the three-way valves 1193, 1195 are completely turned so as to allowflow only through the geothermal loop.

FIG. 13 represents Stage 3B in which both the geothermal cooling 1199and ambient air cooling loops 1197 are active. Pump-2 1255 is ON, theoutside heat exchanger 103 (and fan 105 if present) is/are ON and thethree-way valves are partially turned so as to allow flow through boththe geothermal and ambient air cooling loops.

FIG. 14 represents Stage 3C in which only the ambient air cooling loop1197 is active and the geothermal loop 1199 is inactive. The outsideheat exchanger 103 (and fan 105 if present) is/are ON and the three-wayvalves are completely turned to allow flow only through the ambient aircooling loop 1197. Since there is no flow through the geothermal loop,Pump-2 1255 remains OFF.

FIG. 15 is a flowchart 1500 that illustrates an exemplary operationaltechnique for the embodiment of FIGS. 11-14. The cooling system can beinitiated from any stage; however, for simplicity, Stage 3A (FIG. 12) isrepresented as the initial state of the cooling system, as per step1502. The outdoor air temperature, the ground temperature and thetemperature of the liquid entering the data center system are constantlymonitored and based on these temperatures, different stages can beactivated. When the temperature of the liquid entering the data centeris higher than the maximum allowed temperature (T₁) (“N” branch ofdecision block 1504), the geothermal loop only is not capable ofdissipating the heat to the surroundings and that the cooling systemrequires a different stage of operation (otherwise, as per the “Y”branch, continue in Stage 3A as per 1505).

Following the “N” branch of block 1504, as per decision block 1506, acheck is made whether the outside air temperature is higher than theground temperature. If yes, as per the “Y” branch of block 1506, theambient air cooling loop will also be activated (that is, Stage 3B, FIG.13), as per step 1508. On the other hand, if the outside air temperatureis not higher than the ground temperature, as per the “N” branch ofdecision block 1506, the ambient air cooling loop will be activated andthe geothermal loop will be deactivated (that is, Stage 3C, FIG. 14), asper step 1510. If at this stage, the temperature of the liquid enteringthe data center is higher than the maximum allowed temperature (T₁), asper the “N” branch of decision block 1512, then, the ambient air coolingloop only is also not capable of dissipating the heat to thesurroundings and the cooling system requires the dual (hybrid) stage ofoperation (that is, Stage 3B, FIG. 13), as per step 1508 (otherwise, asper the “Y” branch, continue in Stage 3C as per 1513). Once the systemis in the hybrid mode of operation, it will continually check whetherthe temperature of the liquid entering the data center system is higherthan a minimum temperature (T₂), as per decision block 1514 (if higherthan minimum, keep checking as per “N” branch of block 1514). If not, asper the “Y” branch of decision block 1514, either of the other two modeswill be activated based on the outdoor air and ground temperature. Inparticular, if the ground temperature is not less than the outsidetemperature, as per the “N” branch of decision block 1516, proceed tostep 1510; otherwise, proceed to step 1518 via the “Y” branch of block1516. The switching between different modes of operation can take placeN number of times a year depending upon location of the system, weatherconditions of the location, and other environmental factors.

FIG. 16 shows another alternative embodiment in a series arrangement ina liquid cooled data center with an air side outdoor heat exchanger. Thesystem being cooled includes a liquid cooled rack 104 and a side carsegment 106 and is present inside the data center. The liquid pump 111can either be placed inside the data center unit or outside. Similar tothe previous design, the geothermal loop 1199 in this particularconfiguration uses the ground water for dissipating the system heat tothe surroundings. The geothermal loop is connected to the ambient aircooling loop 1197 in a series arrangement with the help of three-wayvalves 1693, 1695. These three-way valves can be computer controlled. Incase of computer controlled three-way valves, the outside airtemperature, the ground temperature and the temperature of the liquidentering the data center system can be used as control parameters forthe three-way valve control technique. The working of this particularimplementation is schematically explained through FIGS. 17-20. As notedabove, in a preferred approach, there are two temperature sensors—one atthe inlet to the outside air heat exchanger and the other at the outletfrom the outside air heat exchanger. These two sensors will be used tomonitor the amount of heat dissipated to the outside air through theheat exchanger. Also based on this information the position of thethree-way valve can be controlled.

Non-limiting examples of coolants include water and glycol. FIG. 16represents an open loop geothermal cooling series arrangement.Geothermal coil 187 is used to dissipate heat below ground level. In atleast some cases, groundwater is taken from at least 2 m below groundlevel. The ground level temperature may vary, for example, from about 42F to about 80 F, depending on location. See discussion with respect toFIG. 34 below.

FIG. 17 represents Stage 4A in which only the geothermal loop 1199 isactive and the ambient air cooling loop 1197 is inactive. Pump-2 1255 isON, the outside heat exchanger 103 (and fan 105 if present) is/are OFFand the three-way valves are completely turned so as to allow flowthrough the geothermal loop.

FIG. 18 represents Stage 4B in which both the geothermal cooling andambient air cooling loops are active. Pump-2 1255 is ON, the outsideheat exchanger 103 (and fan 105 if present) is/are ON and the three-wayvalves are completely turned so as to allow flow through both thegeothermal and ambient air cooling loops.

FIG. 19 represents Stage 4C in which only the ambient air cooling loopis active and the geothermal loop is inactive. The outside heatexchanger 103 (and fan 105 if present) is/are ON and the three-wayvalves are completely turned to stop the flow through the geothermalcooling loop and to allow flow only through the ambient air coolingloop. Since there no flow through the geothermal loop, Pump-2 1255remains OFF.

FIG. 20 is a flowchart 2000 that illustrates an exemplary operationaltechnique for the embodiment of FIGS. 16-19. The cooling system can beinitiated from any stage, however for simplicity; Stage 4A (FIG. 17) isrepresented as the initial state of the cooling system, as per step2002. The outdoor air temperature, the ground temperature and thetemperature of the liquid entering the data center system are constantlymonitored and based on these temperatures, different stages can beactivated. When the temperature of the liquid entering the data centeris higher than the maximum allowed temperature (T₁) (“N” branch ofdecision block 2004), the geothermal loop only is not capable ofdissipating the heat to the surroundings and the cooling system requiresa different stage of operation (otherwise, as per the “Y” branch,continue in Stage 4A as per 2005). In this situation, a check is madewhether the outside air temperature is higher than the groundtemperature, as at decision block 2006. If yes, as per the “Y” branch ofblock 2006, the ambient air cooling loop will also be activated (thatis, Stage 4B, FIG. 18), as per step 2008. If no, as per the “N” branchof decision block 2006, the ambient air cooling loop will be activatedand the geothermal loop will be deactivated (that is, Stage 4C, FIG.19), as per step 2010. If at this stage, the temperature of the liquidentering the data center is higher than the maximum allowed temperature(T₁), as per the “N” branch of decision block 2012, then, the ambientair cooling loop only is also not capable of dissipating the heat to thesurrounding and the cooling system requires the dual stage of operation(that is, Stage 4B, FIG. 18), as per step 2008 (otherwise, as per the“Y” branch, continue in Stage 4C as per 2013). Once the system is inhybrid mode of operation, it will continually check whether thetemperature of the liquid entering the data center system is higher thana minimum temperature (T₂), as per decision block 2014 (if higher thanminimum, keep checking as per “N” branch of block 2014). If not, as perthe “Y” branch of decision block 2014, either of the other two modeswill be activated based on the outdoor air and ground temperature. Inparticular, if the ground temperature is not less than the outsidetemperature, as per the “N” branch of decision block 2016, proceed tostep 2010; otherwise, proceed to step 2018 via the “Y” branch of block2016. The switching between different modes of operation can take placeN number of times a year depending upon location of the system, weatherconditions of the location, and other environmental factors.

FIG. 21 shows another alternative embodiment in a liquid cooled datacenter with an air side outdoor heat exchanger. The system being cooledincludes a liquid cooled rack 104 and a side car segment 106 and ispresent inside the data center. The liquid pump 111 can either be placedinside the data center unit or outside. The geothermal loop 2199 in thisparticular configuration uses a separate liquid loop 2196 fordissipating the system heat to the surroundings. The geothermal loop isconnected to the ambient air cooling loop 2197 in a parallel arrangementwith the help of three-way valves 2193, 2195. The liquid in the loop2196 could be different from the liquid in the system cooling loop. Thethree-way valves can be computer controlled. In the case of computercontrolled three-way valves, the outside air temperature, the groundtemperature and the temperature of the liquid entering the data centersystem can be used as control parameters for the three-way valve controltechnique. Note that geothermal loop 2199 includes upper loop 2198 andlower (ground) loop 2196 thermally coupled by liquid-to-liquid heatexchanger 2194. The lower loop includes heat exchanger 2192 to rejectheat to the ground temperature. The working of this particularimplementation is schematically explained through FIGS. 22-25. Pleasenote reference character 191 is used herein for both the groundtemperature sensor and ground water temperature sensor.

Non-limiting examples of coolants include water and glycol. FIG. 21represents a closed loop geothermal cooling parallel arrangement.Geothermal coil 2192 is used to dissipate heat below ground level. In atleast some cases, coil 2192 is at least 2 m below ground level. Theground level temperature may vary, for example, from about 42 F to about80 F, depending on location. See discussion with respect to FIG. 34below.

FIG. 22 represents Stage 5A in which only the geothermal loop is activeand the ambient air cooling loop is inactive. Pump-2 1255 is ON, theoutside heat exchanger 103 (and fan 105 if present) is/are OFF and thethree-way valves are completely turned so as to allow flow only throughthe geothermal loop.

FIG. 23 represents Stage 5B in which both the geothermal cooling andambient air cooling loops are active. Pump-2 1255 is ON, the outsideheat exchanger 103 (and fan 105 if present) is/are ON and the three-wayvalves are partially turned so as to allow flow through both thegeothermal and ambient air cooling loops.

FIG. 24 represents Stage 5C in which only the ambient air cooling loopis active and the geothermal loop is inactive. The outside heatexchanger 103 (and fan 105 if present) is/are ON and the three-wayvalves are completely turned to allow flow only through the ambient aircooling loop. Since there no flow through the geothermal loop, Pump-21255 remains OFF.

FIG. 25 is a flowchart 2500 that illustrates an exemplary operationaltechnique for the embodiment of FIGS. 21-24. The cooling system can beinitiated from any stage, however for simplicity; Stage 5A (FIG. 22) isrepresented as the initial state of the cooling system, as per step2502. The outdoor air temperature, the ground temperature and thetemperature of the liquid entering the data center system are constantlymonitored and based on these temperatures, different stages can beactivated. When the temperature of the liquid entering the data centeris higher than the maximum allowed temperature (T₁), as per the “N”branch of decision block 2504, the geothermal loop only is not capableof dissipating the heat to the surroundings and the cooling systemrequires a different stage of operation (otherwise, as per the “Y”branch, continue in Stage 5A as per 2505). In this situation, a check ismade whether the outside air temperature is higher than the groundtemperature, as per decision block 2506. If yes, as per the “Y” branchof decision block 2506, the ambient air cooling loop will also beactivated (that is, Stage 5B, FIG. 23), as per step 2508. If No, as perthe “N” branch of decision block 2506, the ambient air cooling loop willbe activated and the geothermal loop will be deactivated (that is, Stage5C, FIG. 24), as per step 2510. If at this stage, the temperature of theliquid entering the data center is higher than the maximum allowedtemperature (T₁), as per the “N” branch of block 2512, then the ambientair cooling loop only is also not capable of dissipating the heat to thesurrounding and the cooling system requires the dual stage of operation(that is, Stage 5B, FIG. 23), as per step 2508 (otherwise, as per the“Y” branch, continue in Stage 5C as per 2513). Once the system is in thehybrid mode of operation, it will continually check whether thetemperature of the liquid entering the data center system is higher thana minimum temperature (T₂), as per decision block 2514 (if higher thanminimum, keep checking as per “N” branch of block 2514). If not, as perthe “Y” branch of decision block 2514, either of the other two modeswill be activated based on the outdoor air and ground temperature. Inparticular, if the ground temperature is not less than the outsidetemperature, as per the “N” branch of decision block 2516, proceed tostep 2510; otherwise, proceed to step 2518 via the “Y” branch of block2516. The switching between different modes of operation can take placeN number of times a year depending upon location of the system, weatherconditions of the location, and other environmental factors.

FIG. 26 shows another alternative embodiment in a liquid cooled datacenter in a series arrangement with an air side outdoor heat exchanger.The system being cooled includes a liquid cooled rack 104 and a side carsegment 106 and is present inside the data center. The liquid pump 111can either be placed inside the data center unit or outside. Similar tothe previous design, the geothermal loop 2199 in this particularconfiguration uses a separate liquid loop 2196 for dissipating thesystem heat to the surroundings. The geothermal loop and is connected tothe ambient air cooling loop 2197 in a series arrangement with the helpof 3-way valves 2693, 2695. The liquid in the loop 2196 could bedifferent from the liquid in the system cooling loop. These three-wayvalves can be computer controlled. In case of computer controlledthree-way valves, the outside air temperature, the ground temperatureand the temperature of the liquid entering the data center system can beused as control parameters for the three-way valve control technique.The working of this particular implementation is schematically explainedthrough FIGS. 27-30.

Non-limiting examples of coolants include water and glycol. FIG. 26represents a closed loop geothermal cooling series arrangement.Geothermal coil 2192 is used to dissipate heat below ground level. In atleast some cases, coil 2192 is at least 2 m below ground level. Theground level temperature may vary, for example, from about 42 F to about80 F, depending on location. See discussion with respect to FIG. 34below.

FIG. 27 represents Stage 6A in which only the geothermal loop is activeand the ambient air cooling loop is inactive. Pump-2 1255 is ON, theoutside heat exchanger is OFF and the three-way valves are completelyturned so as to allow flow through the geothermal loop.

FIG. 28 represents Stage 6B in which both the geothermal cooling andambient air cooling loops are active. Pump-2 1255 is ON, the outsideheat exchanger is ON and the three-way valves are completely turned soas to allow flow through both the geothermal as well as ambient aircooling loop.

FIG. 29 represents Stage 6C in which only the ambient air cooling loopis active and the geothermal loop is inactive. The outside heatexchanger is ON and the three-way valves are completely turned to stopthe flow through the geothermal cooling loop and to allow flow onlythrough the ambient air cooling loop. Since there no flow through thegeothermal loop, Pump-2 1255 remains OFF.

FIG. 30 is a flowchart 3000 that illustrates an exemplary operationaltechnique for the embodiment of FIGS. 26-29. The cooling system can beinitiated from any stage, however for simplicity; Stage 6A (FIG. 27) isrepresented as the initial state of the cooling system, as per step3002. The outdoor air temperature, the ground temperature and thetemperature of the liquid entering the data center system are constantlymonitored and based on these temperatures, different stages can beactivated. When the temperature of the liquid entering the data centeris higher than the maximum allowed temperature (T₁), as per the “N”branch of decision block 3004, the geothermal loop only is not capableof dissipating the heat to the surroundings and the cooling systemrequires a different stage of operation (otherwise, as per the “Y”branch, continue in Stage 6A as per 3005). In this situation, a check ismade whether the outside air temperature is higher than the groundtemperature, as per decision block 3006. If yes, as per the “Y” branchof decision block 3006, the ambient air cooling loop will also beactivated (that is, Stage 6B, FIG. 28), as per step 3008. If No, as perthe “N” branch of decision block 3006, the ambient air cooling loop willbe activated and the geothermal loop will be deactivated (that is, Stage6C, FIG. 29), as per step 3010. If at this stage, the temperature of theliquid entering the data center is higher than the maximum allowedtemperature (T₁), as per the “N” branch of block 3012, then the ambientair cooling loop only is also not capable of dissipating the heat to thesurrounding and the cooling system requires the dual stage of operation(that is, Stage 6B, FIG. 28), as per step 3008 (otherwise, as per the“Y” branch of block 3012, continue in Stage 6C as per 3013). Once thesystem is in the hybrid mode of operation, it will continually checkwhether the temperature of the liquid entering the data center system ishigher than a minimum temperature (T₂), as per decision block 3014 (ifhigher than minimum, keep checking as per “N” branch of block 3014). Ifnot, as per the “Y” branch of decision block 3014, either of the othertwo modes will be activated based on the outdoor air and groundtemperature. In particular, if the ground temperature is not less thanthe outside temperature, as per the “N” branch of decision block 3016,proceed to step 3010; otherwise, proceed to step 3018 via the “Y” branchof block 3016. The switching between different modes of operation cantake place N number of times a year depending upon location of thesystem, weather conditions of the location, and other environmentalfactors.

In addition to the above-described ambient air cooling with geothermalenhancement designs, completely geothermal-based liquid cooled datacenter designs are also possible. FIG. 31 represents a closed loopgeothermal cooling scheme. FIG. 32 represents an open loop groundwater-based geothermal cooling loop design. FIG. 33 represents anotherclosed loop geothermal cooling design that uses a separate liquid loop2196 for dissipating the system heat to the surroundings. The liquid inthe loop 2196 could be different from the liquid in the system coolingloop. In FIGS. 31-33, the pumps and the geothermal loops operatecontinuously, whenever cooling of the data center is required.Non-limiting examples of coolants include water and glycol, in FIGS.31-33 (and in the other figures, as discussed elsewhere).

FIG. 34 shows a typical year round average ground water temperature mapfor the US, in degrees Fahrenheit. Similar data is available for otherlocations around the world. Fahrenheit can be converted to SI(Centigrade) by first subtracting 32 and then multiplying the result by5/9.

For the avoidance of doubt, the outdoor economizer portions depicted inthe figures include a heat exchanger 103 and a fan 105. However, someembodiments could employ outdoor heat exchanger portions without fans.An “outdoor heat exchanger portion” is intended to encompass both anoutdoor heat exchanger with a fan (economizer) and an outdoor heatexchanger without a fan.

One or more embodiments advantageously provide an auxiliary geothermalloop for cooling of data centers.

Aspects of the invention include a method for providing cooling in adata center cooling system, including providing a data center coolingsystem having a geothermal cooling loop and a heat exchanger loop;monitoring outside air temperature, ground temperature and temperatureof a liquid in the data center system; and selectively operating atleast one of the geothermal cooling loop and the heat exchanger loopbased on the monitored temperatures.

Aspects of the invention also include a system for providing cooling ina data center including a geothermal cooling loop; a heat exchangercooling loop; a plurality of temperature sensors for monitoring outsideair temperature, ground temperature and temperature of a liquid at leastone of the cooling loops; and a controller for selectively operating atleast one of the geothermal cooling loop and the heat exchanger loopbased on the monitored temperatures.

One or more embodiments provide one, some, or all of:

-   -   Free cooling using air-side economizer with geothermal assist.    -   Single loop mode where the coolant entering the rack also passes        through the geothermal loop when the geothermal cooling loop is        active. In other words, free cooling without modular coolant        distribution units.    -   Monitoring outside air temperature, ground temperature and        temperature of a liquid in the data center and heat dissipation        from the rack; and selectively operating at least one of the        geothermal cooling loop and the heat exchanger loop based on the        monitored temperatures.    -   A system for providing cooling in a data center including a        geothermal cooling loop; a heat exchanger cooling loop; a        plurality of temperature sensors for monitoring outside air        temperature, ground temperature, temperature of a liquid at        least one of the cooling loops and heat dissipation from the        electronics rack; and a controller for selectively operating at        least one of the geothermal cooling loop and the heat exchanger        loop based on the monitored temperatures.

Again, one or more embodiments provide free cooling (e.g., of electronicracks) with geothermal assist and/or selective operation based onmonitored temperatures.

In one or more embodiments, the IT infrastructure that needs to becooled remains stationary, above ground, in a conventional data center,while the coolant, removing the heat from the IT infrastructure, rejectsthe heat to the cooler underground via a geothermal cooling loop.

Given the discussion thus far, it will be appreciated that, in generalterms, an exemplary method (see, e.g., FIGS. 5, 10, 15, 20, 25, 30),according to an aspect of the invention, includes the step of operatinga data center cooling system in a first mode. The data center coolingsystem has an indoor portion 100 wherein heat is absorbed fromcomponents 104, 106 in the data center by a heat transfer fluid. Thedata center cooling system has an outdoor heat exchanger portion 103 inloops 197, 1197, 2197 and a geothermal heat exchanger portion 199, 1199,2199.

The first mode includes ambient air cooling of the heat transfer fluidin the outdoor heat exchanger portion and/or geothermal cooling of theheat transfer fluid in the geothermal heat exchanger portion. Adetermination is made, based on an appropriate metric, that a switchshould be made from the first mode to a second mode. Responsive to suchdetermination, the data center cooling system is switched to the secondmode. The second mode is different than the first mode. Thepossibilities are as follows:

-   -   if the first mode is geothermal only, the second mode is air        only or air plus geothermal    -   if the first mode is air only, the second mode is geothermal        only or air plus geothermal    -   if the first mode is air plus geothermal, the second mode is air        only or geothermal only

In some cases, the determining step includes determining based on atleast one of time, heat dissipation from the components, outdoor airtemperature, ground heat sink temperature, and temperature of the heattransfer fluid at a predetermined point (e.g., where it enters the datacenter as per 189). As used herein, ground heat sink temperature refersto the ground or ground water temperature as the case may be.

In some cases, the first mode includes geothermal cooling of the heattransfer fluid in the geothermal heat exchanger portion only, as per502, 1002, 1502, 2002, 2502, and 3002. The determining step includescomparing the temperature of the heat transfer fluid at thepredetermined point to a maximum allowable value, as at 504, 1004, 1504,2004, 2504, and 3004. The second mode includes at least the ambient aircooling of the heat transfer fluid in the outdoor heat exchanger portion(e.g., proceed to 510, 1010, 1510, 2010, 2510, 3010 for ambient aircooling only, or proceed to 516, 1016, 1508, 2008, 2508, 3008 for hybridoperation).

In some cases, the first mode includes geothermal cooling of the heattransfer fluid in the geothermal heat exchanger portion only, as per502, 1002, 1502, 2002, 2502, and 3002. The determining step includescomparing the temperature of the heat transfer fluid at thepredetermined point to a maximum allowable value, as at 504, 1004, 1504,2004, 2504, and 3004. The second mode includes both the ambient aircooling of the heat transfer fluid in the outdoor heat exchanger portionand the geothermal cooling of the heat transfer fluid in the geothermalheat exchanger portion (e.g., proceed to 516, 1016, 1508, 2008, 2508,3008 for hybrid operation).

In such cases, additional steps include comparing the temperature of theheat transfer fluid at the predetermined point to a minimum allowablevalue while operating in the second mode, as per 518, 1018, 1514, 2014,2514, 3014; and, responsive to the temperature of the heat transferfluid at the predetermined point being less than the minimum allowablevalue, ceasing one of the ambient air cooling of the heat transfer fluidin the outdoor heat exchanger portion and the geothermal cooling of theheat transfer fluid in the geothermal heat exchanger portion (as per520, 522; 1020, 1022; 1516, 1518; 2016, 2018; 2516, 2518; or 3016;3018).

In some instances, such as FIGS. 1, 11, and 21, the outdoor heatexchanger portion and the geothermal heat exchanger portion are arrangedin parallel, and the second mode includes passing a first fraction offlow of the heat transfer fluid through the outdoor heat exchangerportion and a second fraction of the flow of the heat transfer fluidthrough the geothermal heat exchanger portion (the two fractions add upto 100%). As seen, e.g., in FIG. 1, in some cases, the second modeincludes cooling the second fraction of the flow of the heat transferfluid through the geothermal heat exchanger portion by passing samethrough a coil 187 in contact with earth that is cooler than the heattransfer fluid passing through the geothermal heat exchanger portion. A“coil” should be broadly construed to encompass a variety of heatexchanger types.

As seen, e.g., in FIG. 11, in some cases, the second mode includescooling the second fraction of the flow of the heat transfer fluidthrough the geothermal heat exchanger portion by passing same through aliquid-to-liquid heat exchanger 1194 having a flow of groundwater thatis cooler than the heat transfer fluid passing through the geothermalheat exchanger portion.

As seen, e.g., in FIG. 21, in some cases, the heat transfer fluid is afirst heat transfer fluid and the second mode includes cooling thesecond fraction of the flow of the first heat transfer fluid through thegeothermal heat exchanger portion by passing same through aliquid-to-liquid heat exchanger 2194 having a flow of a second heattransfer fluid that is cooler than the first heat transfer fluid passingthrough the geothermal heat exchanger portion (second heat transferfluid can be same or different than first heat transfer fluid and ispumped through loop 2196 by Pump-2 1255). The second heat transfer fluidis cooled by passing same through a coil 2192 in contact with earth thatis cooler than the second heat transfer fluid.

In some instances, such as FIGS. 6, 16, and 26, the outdoor heatexchanger portion and the geothermal heat exchanger portion are arrangedin series, and the second mode includes passing the entire flow of theheat transfer fluid through the outdoor heat exchanger portion and thegeothermal heat exchanger portion. In some cases, such as FIG. 6, thesecond mode includes cooling the flow of the heat transfer fluid throughthe geothermal heat exchanger portion by passing same through a coil 187in contact with earth that is cooler than the heat transfer fluidthrough the geothermal heat exchanger portion.

In some cases, such as FIG. 16, the second mode includes cooling theflow of the heat transfer fluid through the geothermal heat exchangerportion by passing same through a liquid-to-liquid heat exchanger 1194having a flow of groundwater that is cooler than the heat transfer fluidthrough the geothermal heat exchanger portion.

In some cases, such as FIG. 26, the heat transfer fluid is a first heattransfer fluid, and the second mode includes cooling the flow of theheat transfer fluid through the geothermal heat exchanger portion bypassing same through a liquid-to-liquid heat exchanger 2194 having aflow of a second heat transfer fluid that is cooler than the first heattransfer fluid passing through the geothermal heat exchanger portion(second heat transfer fluid can be same or different than first heattransfer fluid and is pumped through loop 2196 by Pump-2 1255). Thesecond heat transfer fluid is cooled by passing same through a coil 2192in contact with earth that is cooler than the second heat transferfluid.

In another aspect, an exemplary data center cooling system includes anindoor portion 100 wherein heat is absorbed from components 104, 106 inthe data center by a heat transfer fluid; an outdoor heat exchangerportion 103 in loops 197, 1197, 2197 and a geothermal heat exchangerportion 199, 1199, 2199. The outdoor heat exchanger portion andgeothermal heat exchanger portion are in selective fluid communicationwith the indoor portion. Also included is a valve arrangement (e.g.,193, 195; 693, 695; 1193, 1195; 1693, 1695; 2193, 2195; 2693, 2695)configured to switch the data center cooling system between first andsecond modes of operation.

The first and second modes have been discussed above in connection withthe exemplary method.

In some cases, the system also includes a control unit (see discussionof FIG. 35 below) coupled to the valve arrangement and configured todetermine, based on an appropriate metric, that a switch should be madefrom the first mode to the second mode (using, e.g., the computer ofFIG. 35 programmed with the logic in the flow charts). The valvearrangement switches the system to the second mode responsive to thedetermination by the control unit.

In a non-limiting example, the control unit includes outdoor airtemperature sensor 109, coolant temperature sensor 189, and ground (orgroundwater) temperatures sensor 191. The sensor could be, for example,a thermocouple or the like coupled to logic in a processor as describedbelow with regard to FIG. 35. Mechanical or electromechanicaltechniques, such as a bimetallic strip with contacts, could also beused. Appropriate logic, such as described with regard to FIG. 35, couldalso be used to implement any of the other approaches, such asdetermining that a particular calendar day has been reached (calendar orclock logic in machine 3512), making a determination based on localmeteorological data (e.g., interface to a weather web site orprogramming based on historical data), and the like.

In some cases, the control unit makes the determination based on atleast one of time, heat dissipation from the components, outdoor airtemperature, ground heat sink temperature (defined above), andtemperature of the heat transfer fluid at a predetermined point.

In some cases, as discussed above with respect to the exemplary method,the first mode includes geothermal cooling of the heat transfer fluid inthe geothermal heat exchanger portion only; the control unit makes thedetermination by comparing the temperature of the heat transfer fluid atthe predetermined point to a maximum allowable value; and the secondmode includes at least the ambient air cooling of the heat transferfluid in the outdoor heat exchanger portion.

In some cases, as discussed above with respect to the exemplary method,the first mode includes geothermal cooling of the heat transfer fluid inthe geothermal heat exchanger portion only; the control unit makes thedetermination by comparing the temperature of the heat transfer fluid atthe predetermined point to a maximum allowable value; and the secondmode includes the ambient air cooling of the heat transfer fluid in theoutdoor heat exchanger portion and the geothermal cooling of the heattransfer fluid in the geothermal heat exchanger portion. Again, asdiscussed above with respect to the exemplary method, the control unitcompares the temperature of the heat transfer fluid at the predeterminedpoint to a minimum allowable value while operating in the second mode;and, responsive to the temperature of the heat transfer fluid at thepredetermined point being less than the minimum allowable value, thecontrol unit operates the valve arrangement to cease one of the ambientair cooling of the heat transfer fluid in the outdoor heat exchangerportion and the geothermal cooling of the heat transfer fluid in thegeothermal heat exchanger portion.

As also discussed above with respect to the exemplary method, in somecases, such as FIGS. 1, 11, and 21, the outdoor heat exchanger portionand the geothermal heat exchanger portion are arranged in parallel, andthe valve arrangement is configured to, during the second mode, pass afirst fraction of flow of the heat transfer fluid through the outdoorheat exchanger portion and a second fraction of the flow of the heattransfer fluid through the geothermal heat exchanger portion. Forexample, as seen in FIG. 1, in some cases, the geothermal heat exchangerportion includes a coil 187 in contact with earth; and the valvearrangement is configured to, during the second mode, cause the secondfraction of the flow of the heat transfer fluid through the geothermalheat exchanger portion to pass through the coil.

In some cases, such as FIG. 11, the geothermal heat exchanger portionincludes a liquid-to-liquid heat exchanger 1194 having a flow ofgroundwater; and the valve arrangement is configured to, during thesecond mode, cause the second fraction of the flow of the heat transferfluid through the geothermal heat exchanger portion to pass through theliquid-to-liquid heat exchanger 1194.

In some cases, such as FIG. 21, the heat transfer fluid is a first heattransfer fluid; and the geothermal heat exchanger portion includes aliquid-to-liquid heat exchanger 2194 having a flow of a second heattransfer fluid; and a coil 2192 in contact with earth; such coil is influid communication with the second heat transfer fluid in theliquid-to-liquid heat exchanger. The valve arrangement is configured to,during the second mode, cause the second fraction of the flow of theheat transfer fluid through the geothermal heat exchanger portion topass through the liquid-to-liquid heat exchanger.

As also discussed above with respect to the exemplary method, in somecases, such as FIGS. 6, 16, and 26, the outdoor heat exchanger portionand the geothermal heat exchanger portion are arranged in series, andthe valve arrangement is configured to, during the second mode, pass theentire flow of the heat transfer fluid through the outdoor heatexchanger portion and the geothermal heat exchanger portion.

For example, as seen in FIG. 6, in some cases, the geothermal heatexchanger portion includes a coil 187 in contact with earth; and thevalve arrangement is configured to, during the second mode, cause theflow of the heat transfer fluid through the geothermal heat exchangerportion to pass through the coil.

For example, as seen in FIG. 16, in some cases, the geothermal heatexchanger portion includes a liquid-to-liquid heat exchanger 1194 havinga flow of groundwater; and the valve arrangement is configured to,during the second mode, cause the flow of the heat transfer fluidthrough the geothermal heat exchanger portion to pass through theliquid-to-liquid heat exchanger.

For example, as seen in FIG. 26, in some cases, the heat transfer fluidincludes a first heat transfer fluid; and the geothermal heat exchangerportion includes a liquid-to-liquid heat exchanger 2194 having a flow ofa second heat transfer fluid; and a coil 2192 in contact with earth,which coil is in fluid communication with the second heat transfer fluidin the liquid-to-liquid heat exchanger. Furthermore, the valvearrangement is configured to, during the second mode, cause the flow ofthe heat transfer fluid through the geothermal heat exchanger portion topass through the liquid-to-liquid heat exchanger.

In another aspect, a data center cooling system (FIGS. 31-33) includesan indoor portion wherein heat is absorbed from electronic components(e.g., in the rack 104) in the data center by a heat transfer fluid; anda geothermal heat exchanger portion (e.g., 187; 1194, 1196, 1255; 2194,2196, 2192, 1255) in thermal communication with the indoor portion andconfigured to reject the heat to at least one of earth (FIGS. 31 and 33)and groundwater (FIG. 32). Methods of operating such a system includepumping a fluid through a heat exchanger (rack and/or side car) toabsorb heat from electronic components; and rejecting such heat togroundwater and/or earth, either directly or via a liquid-to-liquid heatexchanger with groundwater or a second loop.

Exemplary System and Article of Manufacture Details

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or computer programproduct. Accordingly, aspects of the present invention may take the formof an entirely hardware embodiment, an entirely software embodiment(including firmware, resident software, micro-code, etc.) or anembodiment combining software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”Furthermore, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon. Forthe avoidance of doubt, most embodiments include physical heat transferand fluid flow hardware which may be computer controlled, controlled byhumans, controlled by electromechanical and/or bimetallic controllers,and the like; a software embodiment could include, for example, acomputer readable storage medium with instructions for system controland/or design functionality.

One or more embodiments of the invention, or elements thereof, can beimplemented in the form of an apparatus including a memory and at leastone processor that is coupled to the memory and operative to performexemplary method steps.

One or more embodiments can make use of software running on a generalpurpose computer or workstation. With reference to FIG. 35, such animplementation might employ, for example, a processor 3502, a memory3504, and an input/output interface formed, for example, by a display3506 and a keyboard 3508. The term “processor” as used herein isintended to include any processing device, such as, for example, onethat includes a CPU (central processing unit) and/or other forms ofprocessing circuitry. Further, the term “processor” may refer to morethan one individual processor. The term “memory” is intended to includememory associated with a processor or CPU, such as, for example, RAM(random access memory), ROM (read only memory), a fixed memory device(for example, hard drive), a removable memory device (for example,diskette), a flash memory and the like. In addition, the phrase“input/output interface” as used herein, is intended to include, forexample, one or more mechanisms for inputting data to the processingunit (for example, mouse), and one or more mechanisms for providingresults associated with the processing unit (for example, printer). Theprocessor 3502, memory 3504, and input/output interface such as display3506 and keyboard 3508 can be interconnected, for example, via bus 3510as part of a data processing unit 3512. Suitable interconnections, forexample via bus 3510, can also be provided to a network interface 3514,such as a network card, which can be provided to interface with acomputer network, and to a media interface 3516, such as a diskette orCD-ROM drive, which can be provided to interface with media 3518.

Suitable interfaces can be provided to receive signals from sensors(e.g., temperature, pressure, flow rate, heat dissipation, and/or valveposition sensors) and/or to send signals to actuators for valves, vents,fans, and the like. These could be provided over network interface 3514and/or via separate sensor interface 3597 and/or separate actuatorinterface 3599, including, for example, suitable digital-to-analogand/or analog-to-digital converters.

Accordingly, computer software including instructions or code forperforming the methodologies of the invention, as described herein, maybe stored in one or more of the associated memory devices (for example,ROM, fixed or removable memory) and, when ready to be utilized, loadedin part or in whole (for example, into RAM) and implemented by a CPU.Such software could include, but is not limited to, firmware, residentsoftware, microcode, and the like.

A data processing system suitable for storing and/or executing programcode will include at least one processor 3502 coupled directly orindirectly to memory elements 3504 through a system bus 3510. The memoryelements can include local memory employed during actual implementationof the program code, bulk storage, and cache memories which providetemporary storage of at least some program code in order to reduce thenumber of times code must be retrieved from bulk storage duringimplementation.

Input/output or I/O devices (including but not limited to keyboards3508, displays 3506, pointing devices, and the like) can be coupled tothe system either directly (such as via bus 3510) or through interveningI/O controllers (omitted for clarity).

Network adapters such as network interface 3514 may also be coupled tothe system to enable the data processing system to become coupled toother data processing systems or remote printers or storage devicesthrough intervening private or public networks. Modems, cable modem andEthernet cards are just a few of the currently available types ofnetwork adapters.

As used herein, including the claims, a “server” includes a physicaldata processing system (for example, system 3512 as shown in FIG. 35)running a server program. It will be understood that such a physicalserver may or may not include a display and keyboard.

As noted, aspects of the present invention may take the form of acomputer program product embodied in one or more computer readablemedium(s) having computer readable program code embodied thereon. Anycombination of one or more computer readable medium(s) may be utilized.The computer readable medium may be a computer readable signal medium ora computer readable storage medium. A computer readable storage mediummay be, for example, but not limited to, an electronic, magnetic,optical, electromagnetic, infrared, or semiconductor system, apparatus,or device, or any suitable combination of the foregoing. Media block3518 is a non-limiting example. More specific examples (a non-exhaustivelist) of the computer readable storage medium would include thefollowing: an electrical connection having one or more wires, a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), an optical fiber, a portable compact disc read-onlymemory (CD-ROM), an optical storage device, a magnetic storage device,or any suitable combination of the foregoing. In the context of thisdocument, a computer readable storage medium may be any tangible mediumthat can contain, or store a program for use by or in connection with aninstruction execution system, apparatus, or device.

A computer readable signal medium may include a propagated data signalwith computer readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Acomputer readable signal medium may be any computer readable medium thatis not a computer readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a computer readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thepresent invention may be written in any combination of one or moreprogramming languages, including an object oriented programming languagesuch as Java, Smalltalk, C++ or the like and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on theuser's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough any type of network, including a local area network (LAN) or awide area network (WAN), or the connection may be made to an externalcomputer (for example, through the Internet using an Internet ServiceProvider).

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions, which execute via theprocessor of the computer or other programmable data processingapparatus, create means for implementing the functions/acts specified inthe flowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerreadable medium that can direct a computer, other programmable dataprocessing apparatus, or other devices to function in a particularmanner, such that the instructions stored in the computer readablemedium produce an article of manufacture including instructions whichimplement the function/act specified in the flowchart and/or blockdiagram block or blocks.

The computer program instructions may also be loaded onto a computer,other programmable data processing apparatus, or other devices to causea series of operational steps to be performed on the computer, otherprogrammable apparatus or other devices to produce a computerimplemented process such that the instructions which execute on thecomputer or other programmable apparatus provide processes forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

It should be noted that any of the methods described herein can includean additional step of providing a system comprising distinct softwaremodules embodied on a computer readable storage medium; the modules caninclude, for example, one or more distinct software modules for control(e.g., to control the cooling systems using the logic in the flowcharts) and/or system design. The method steps can then be carried out,or at least facilitated by, using the distinct software modules and/orsub-modules of the system, as described above, executing on one or morehardware processors 3502. Further, a computer program product caninclude a computer-readable storage medium with code adapted to beimplemented to carry out one or more method steps described herein,including the provision of the system with the distinct softwaremodules.

In any case, it should be understood that the components illustratedherein may be implemented in various forms of hardware, software, orcombinations thereof; for example, application specific integratedcircuit(s) (ASICS), functional circuitry, one or more appropriatelyprogrammed general purpose digital computers with associated memory, andthe like. Given the teachings of the invention provided herein, one ofordinary skill in the related art will be able to contemplate otherimplementations of the components of the invention.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. The corresponding structures,materials, acts, and equivalents of all means or step plus functionelements in the claims below are intended to include any structure,material, or act for performing the function in combination with otherclaimed elements as specifically claimed. The description of the presentinvention has been presented for purposes of illustration anddescription, but is not intended to be exhaustive or limited to theinvention in the form disclosed. Many modifications and variations willbe apparent to those of ordinary skill in the art without departing fromthe scope and spirit of the invention. The embodiment was chosen anddescribed in order to best explain the principles of the invention andthe practical application, and to enable others of ordinary skill in theart to understand the invention for various embodiments with variousmodifications as are suited to the particular use contemplated.

What is claimed is:
 1. A method comprising: operating a data centercooling system in a first mode, said data center cooling system havingan indoor portion wherein heat is absorbed from components in said datacenter by a heat transfer fluid, said data center cooling system havingan outdoor heat exchanger portion and a geothermal heat exchangerportion, said first mode comprising at least one of: ambient air coolingof said heat transfer fluid in said outdoor heat exchanger portion; andgeothermal cooling of said heat transfer fluid in said geothermal heatexchanger portion; determining, based on an appropriate metric, that aswitch should be made from said first mode to a second mode; andresponsive to said determining, switching said data center coolingsystem to said second mode, said second mode being different than saidfirst mode, said second mode comprising at least another one of: ambientair cooling of said heat transfer fluid in said outdoor heat exchangerportion; and geothermal cooling of said heat transfer fluid in saidgeothermal heat exchanger portion; wherein said determining stepcomprises determining based on at least one of time, heat dissipationfrom said components, outdoor air temperature, ground heat sinktemperature, and temperature of said heat transfer fluid at apredetermined point; wherein: said first mode comprises geothermalcooling of said heat transfer fluid in said geothermal heat exchangerportion only; said determining step comprises comparing said temperatureof said heat transfer fluid at said predetermined point to a maximumallowable value; and said second mode comprises said ambient air coolingof said heat transfer fluid in said outdoor heat exchanger portion andsaid geothermal cooling of said heat transfer fluid in said geothermalheat exchanger portion; further comprising: comparing said temperatureof said heat transfer fluid at said predetermined point to a minimumallowable value while operating in said second mode; and responsive tosaid temperature of said heat transfer fluid at said predetermined pointbeing less than said minimum allowable value, ceasing one of saidambient air cooling of said heat transfer fluid in said outdoor heatexchanger portion and said geothermal cooling of said heat transferfluid in said geothermal heat exchanger portion; wherein said outdoorheat exchanger portion and said geothermal heat exchanger portion arearranged in parallel, and wherein said second mode comprises passing afirst fraction of flow of said heat transfer fluid through said outdoorheat exchanger portion and a second fraction of said flow of said heattransfer fluid through said geothermal heat exchanger portion; andwherein said second mode comprises cooling said second fraction of saidflow of said heat transfer fluid through said geothermal heat exchangerportion by passing same through a liquid-to-liquid heat exchanger havinga flow of groundwater that is cooler than said heat transfer fluidpassing through said geothermal heat exchanger portion.
 2. A methodcomprising: operating a data center cooling system in a first mode, saiddata center cooling system having an indoor portion wherein heat isabsorbed from components in said data center by a heat transfer fluid,said data center cooling system having an outdoor heat exchanger portionand a geothermal heat exchanger portion, said first mode comprising atleast one of: ambient air cooling of said heat transfer fluid in saidoutdoor heat exchanger portion; and geothermal cooling of said heattransfer fluid in said geothermal heat exchanger portion; determining,based on an appropriate metric, that a switch should be made from saidfirst mode to a second mode; and responsive to said determining,switching said data center cooling system to said second mode, saidsecond mode being different than said first mode, said second modecomprising at least another one of: ambient air cooling of said heattransfer fluid in said outdoor heat exchanger portion; and geothermalcooling of said heat transfer fluid in said geothermal heat exchangerportion; wherein said determining step comprises determining based on atleast one of time, heat dissipation from said components, outdoor airtemperature, ground heat sink temperature, and temperature of said heattransfer fluid at a predetermined point; wherein: said first modecomprises geothermal cooling of said heat transfer fluid in saidgeothermal heat exchanger portion only; said determining step comprisescomparing said temperature of said heat transfer fluid at saidpredetermined point to a maximum allowable value; and said second modecomprises said ambient air cooling of said heat transfer fluid in saidoutdoor heat exchanger portion and said geothermal cooling of said heattransfer fluid in said geothermal heat exchanger portion; furthercomprising: comparing said temperature of said heat transfer fluid atsaid predetermined point to a minimum allowable value while operating insaid second mode; and responsive to said temperature of said heattransfer fluid at said predetermined point being less than said minimumallowable value, ceasing one of said ambient air cooling of said heattransfer fluid in said outdoor heat exchanger portion and saidgeothermal cooling of said heat transfer fluid in said geothermal heatexchanger portion; wherein said outdoor heat exchanger portion and saidgeothermal heat exchanger portion are arranged in parallel, and whereinsaid second mode comprises passing a first fraction of flow of said heattransfer fluid through said outdoor heat exchanger portion and a secondfraction of said flow of said heat transfer fluid through saidgeothermal heat exchanger portion; and wherein said heat transfer fluidcomprises a first heat transfer fluid, and wherein said second modecomprises: cooling said second fraction of said flow of said first heattransfer fluid through said geothermal heat exchanger portion by passingsame through a liquid-to-liquid heat exchanger having a flow of a secondheat transfer fluid that is cooler than said first heat transfer fluidpassing through said geothermal heat exchanger portion; and cooling saidsecond heat transfer fluid by passing same through a coil in contactwith earth that is cooler than said second heat transfer fluid.
 3. Amethod comprising: operating a data center cooling system in a firstmode, said data center cooling system having an indoor portion whereinheat is absorbed from components in said data center by a heat transferfluid, said data center cooling system having an outdoor heat exchangerportion and a geothermal heat exchanger portion, said first modecomprising at least one of: ambient air cooling of said heat transferfluid in said outdoor heat exchanger portion; and geothermal cooling ofsaid heat transfer fluid in said geothermal heat exchanger portion;determining, based on an appropriate metric, that a switch should bemade from said first mode to a second mode; and responsive to saiddetermining, switching said data center cooling system to said secondmode, said second mode being different than said first mode, said secondmode comprising at least another one of: ambient air cooling of saidheat transfer fluid in said outdoor heat exchanger portion; andgeothermal cooling of said heat transfer fluid in said geothermal heatexchanger portion; wherein said determining step comprises determiningbased on at least one of time, heat dissipation from said components,outdoor air temperature, ground heat sink temperature, and temperatureof said heat transfer fluid at a predetermined point; wherein: saidfirst mode comprises geothermal cooling of said heat transfer fluid insaid geothermal heat exchanger portion only; said determining stepcomprises comparing said temperature of said heat transfer fluid at saidpredetermined point to a maximum allowable value; and said second modecomprises said ambient air cooling of said heat transfer fluid in saidoutdoor heat exchanger portion and said geothermal cooling of said heattransfer fluid in said geothermal heat exchanger portion; furthercomprising: comparing said temperature of said heat transfer fluid atsaid predetermined point to a minimum allowable value while operating insaid second mode; and responsive to said temperature of said heattransfer fluid at said predetermined point being less than said minimumallowable value, ceasing one of said ambient air cooling of said heattransfer fluid in said outdoor heat exchanger portion and saidgeothermal cooling of said heat transfer fluid in said geothermal heatexchanger portion; wherein said outdoor heat exchanger portion and saidgeothermal heat exchanger portion are arranged in series, and whereinsaid second mode comprises passing an entire flow of said heat transferfluid through said outdoor heat exchanger portion and said geothermalheat exchanger portion.
 4. The method of claim 3, wherein said secondmode comprises cooling said flow of said heat transfer fluid throughsaid geothermal heat exchanger portion by passing same through a coil incontact with earth that is cooler than said heat transfer fluid throughsaid geothermal heat exchanger portion.
 5. The method of claim 3,wherein said second mode comprises cooling said flow of said heattransfer fluid through said geothermal heat exchanger portion by passingsame through a liquid-to-liquid heat exchanger having a flow ofgroundwater that is cooler than said heat transfer fluid through saidgeothermal heat exchanger portion.
 6. The method of claim 3, whereinsaid heat transfer fluid comprises a first heat transfer fluid, andwherein said second mode comprises: cooling said flow of said heattransfer fluid through said geothermal heat exchanger portion by passingsame through a liquid-to-liquid heat exchanger having a flow of a secondheat transfer fluid that is cooler than said first heat transfer fluidpassing through said geothermal heat exchanger portion; and cooling saidsecond heat transfer fluid by passing same through a coil in contactwith earth that is cooler than said second heat transfer fluid.